Exoplanet Characterization

As an undergraduate, I lead a team of 21 researchers from 12 institutions in an a worldwide effort to characterize the atmosphere and physical and dynamical properties of the warm-Neptune GJ 3470b (Biddle et al. 2014). I coordinated a team of scientists through remote communications, and I managed the development of the written paper to completion. The program delivered the largest set of homogeneously analyzed transits of GJ 3470b at the time, producing an updated transmission spectrum that reinforced the existence of an H2-dominated atmosphere and a strong Rayleigh scattering slope. This work also yielded the

Transmission spectrum of GJ 3470 b published in Biddle et al. (2014).

most precise measurement of the planet radius yet, as well as an updated limit on the planet mass and an improved orbital ephemeris. Results also included refined measurements of the host star’s temperature, mass, radius, metallicity, logg, and rotation, crucial to knowing thy star. How well we can characterize a planet is limited by how well we know the star, driving the argument that stellar characterization campaigns should be a priority in the field of exoplanets.


Steps outlining the image-processing procedure used to autonomously detect the leading edge of Coronal Mass Ejections for STEREO Heliospheric Imagers.

Autonomous CME Detection

I completed an REU mentored by Dr. Tim Howard at the Laboratory for Atmospheric Space Physics (LASP) and the Southwest Research Institute (SwRI), where I developed an algorithmic procedure in IDL to autonomously detect solar coronal mass ejections (CMEs) in images compatible with Heliospheric Imagers aboard the Solar Terrestrial Relations Observatory (STEREO) spacecraft. The coordinates

could then be used to reconstruct the 3D profile of the CME enabling more advanced characterization of these energetic and potentially hazardous events.

AGN Accretion Characteristics

As a post-baccalaureate intern mentored by Dr. Rachel Mason at Gemini Observatory, I analyzed a subset of 34 cross-dispersed spectra of nearby galaxies (0.8 – 2.5 μm) taken at Gemini North with the Gemini Near-Infrared Spectrograph (GNIRS) to investigate the degree to which the accretion disk and hot dust emission of active galactic nuclei (AGN) depend on the luminosity of the nucleus. I prepared, reduced, and extracted the XD spectra using the GNIRS PyRAF/IRAF pipeline , and then for each target I subtracted the off-nucleus spectrum from the AGN spectrum, separating the AGN emission from the stellar emission. I fit the residual spectrum with a combination of blackbody profiles to determine the temperature of the AGN which I then used to calculate the luminosity of the nucleus. We found that for objects with low accretion rates, the surrounding disk could become truncated and its inner region may be replaced by an advection-dominated accretion flow.

Protoplanetary Disk Lifetimes

The primary mechanism that regulates the lifetime of protoplanetary disks is still undetermined, and is a crucial component to understanding the conditions in which planets can, or cannot, form. Young binaries are excellent laboratories for studying disk lifetimes because the components are coeval, allowing us to test mechanisms for disk evolution with the stellar age as a control. For my Master’s degree, I presented a case study analysis characterizing the relative orientation and rotational properties of the young binary DF Tau (Allen et al. 2017). DF Tau is a ∼2 Myr old binary of equal mass and separation of ∼15 au. The primary component retained its circumstellar disk, while the secondary component did not, making it ideal to test sources that drive disk-loss.